A housing includes a first opening and a second opening, and encloses a light-emitting element, a first light receiving unit, and a second light receiving unit. The first opening is provided in a first light guide path arranged between the light-emitting element and a first irradiated region of the target surface, and is arranged so that light output from the light-emitting element travels toward the first irradiated region. The second opening is provided in a second light guide path arranged between the first irradiated region and the first light receiving unit, and is arranged so that diffused reflection light from the toner image passes through when the toner image passes the first irradiated region.

An image forming apparatus includes: an image holder configured to hold an image formed using an electrographic process; a transfer body that faces the image holder and is configured to contact the image holder while rotating to form a secondary transfer region; an application unit configured to apply a voltage for charging the secondary transfer region; and a charge unit that faces a region other than the secondary transfer region of the transfer body and is configured to charge a surface of the transfer body with a polarity opposite to an applied voltage of the application unit.

A measurement device is provided with: a measurement unit including a first mode that measures an electrical resistance of a recording medium used in an image forming apparatus in a first predetermined range of electrical resistance values and a second mode that measures the electrical resistance in a second range of electrical resistance values different from the first range, the second range and the first range being set such that with respect to the electrical resistance of multiple brands of recording media, a number of brands belonging to the second range is greater than a number of brands belonging to the first range; and a control unit that controls the measurement unit to prioritize execution of the second mode over the first mode.

An apparatus comprising a first control unit that executes density correction processing on image data and generates an image signal, an image forming unit that forms an image on a recording medium on the basis of the image signal, and a second control unit that controls the image forming unit. The first control unit includes a specifying unit that transmits specifying information relating to the density correction processing to the second control unit. The second control unit includes an acquisition unit that acquires a parameter relating to the image forming apparatus, and an estimation unit that estimates a plurality of image densities corresponding to tone levels identified by the specifying information transmitted from the first control unit on the basis of the parameter acquired by the acquisition unit and transmits the plurality of image densities to the first control unit.

An image forming apparatus includes an image bearing member, an intermediary transfer belt, a transfer member, a voltage source for applying a voltage to the transfer member, a detecting portion for detecting a current flowing through the transfer member, and a controller for carrying out constant-voltage control so that the voltage applied to the transfer member becomes a target voltage when a recording material P passes through a transfer portion. The controller is capable of changing the voltage applied to the transfer member so that a detection result detected by the detecting portion during transfer falls within a predetermined range. The controller changes the predetermined range on the basis of the detection result detected by the detecting portion when the voltage is applied to the transfer member in a state in which the recording material P is absent in the transfer portion.

The image forming apparatus forms a test chart on an image bearing member, the test chart including a plurality of test images including a first test image of a first density and a second test image formed at a position different from a position of the first test image in a conveying direction of a recording medium, the second test image having a second density different from the first density. The image forming apparatus transfers the test chart to the recording medium with a transfer roller and controls the rotation velocity of the transfer roller when the recording medium passes through a transfer portion based on a result of reading the test chart on the recording medium with a reading unit.

An image forming apparatus includes an image bearing member, a transfer member, a moving portion, a driving portion, a voltage applying portion, a first detecting portion, and a second detecting portion. On the basis of a detection result of the first detecting portion when a first test voltage is applied to the transfer member by the voltage applying portion, the second detecting portion sets a second test voltage. The second detecting portion detects a position of the transfer member on the basis of a detection result of a current value by the first detecting portion acquired when the second test voltage is applied to the transfer member by the voltage applying portion.

An image forming apparatus includes an image forming device and circuitry. The image forming device forms an image. The circuitry corrects an amount of deviation based on a pattern formed by the image forming device, changes a magnification of the pattern, and calculates the amount of deviation based on the magnification.

An imaging system includes: a steering roller located between a first belt roller and a second belt roller, that is inclinable around a fulcrum; and a sensor to detect an amount of displacement of the steering roller due to an inclination of the steering roller. A controller may output a command signal when the amount of displacement of the steering roller exceeds a reference value.

An image forming apparatus includes an image forming unit configured to form an image on an image carrier, a transfer unit configured to transfer the image from the image carrier to a sheet, a reader configured to read a pattern image on the sheet while conveying the sheet, a sensor configured to measure a measuring image on the image carrier, and a controller configured to control the image forming unit to form the pattern image and the measuring image while forming images on a plurality of sheets, control the reader to read the pattern image, control the sensor to measure the measuring image, and generate an image forming condition based on a result of reading the pattern image by the reader and a result of measuring the measuring image by the sensor.